1. Field of the Invention
This invention relates to a debris shield to provide a measure of protection to the hull of a spacecraft from impacting space debris.
2. Description of the Prior Art
Space exploration poses a number of risks that are unique and unparalleled on Earth. For example, it is commonly known that there are a vast number of fast moving particles of space debris in the vicinity of the Earth and in the Earth's orbit. This is partially a result of years of launching space vehicles that have left matter that did not reenter the Earth's atmosphere and disintegrate. Another source of this debris is naturally occurring particles such as micro meteors.
Many of these particles have sufficient momentum to penetrate the hull of a spacecraft. In those instances where the craft is not habited, the penetrations could damage or destroy equipment onboard the craft. In case where the spacecraft is inhabited, penetration of the hull can lead to a loss of atmosphere and potentially a loss of human life. In either case, space vehicles need to have protection from impacting space debris.
One method of protecting spacecraft from the potential damage of fast moving space particles has been the use of a “Whipple Shield.” An enhanced Whipple Shield is described in U.S. Pat. No. 5,610,363 to Crews, et al. Basically, a Whipple Shield has a number of particle shocking layers spaced apart and the shield covers the hull of a spacecraft. As a particle impacts a layer of the shield, the particle's kinetic energy is converted by way of the interaction with the shield and this conversion results in the particle being broken into fragments and dispersed in a cone or plume fashion. Each successive layer of the shield continues to break the particles into smaller and smaller debris elements until, ideally, the particle is fragmented into a mist of micro particles and the kinetic energy is either transferred to the shield or over a wide range of extremely small particles moving at substantially lower velocities.
Early Whipple Shields used layers of metals such as aluminum to impact the particles. This had several disadvantages. For example, the shields tended to be very heavy. With launch costs being directly related to weight, this meant that the use of a metal shield was very expensive. Also, The metal layers were rigid and thus the volume of a spacecraft was fixed.
While fixed volume spacecraft using a rigid hull have been used widely, a revolutionary flexible hulled craft is now being developed. An inflatable modular structure is a unique approach at providing a cost effective, large volume, habitable working environment for use in space and on extraterrestrial bodies. This approach is distinct due to the characteristic structure of the module.
The inflatable structure has a truss arrangement predominately surrounded by an inflatable flexible multi-layered shell. This allows for minimizing the volume of the module at launch and maximizing the volume when deployed.
In the pre-deployed configuration, the shell is folded about the truss and secured in such a way that the module can be fitted into the payload section of a conventional launch vehicle. When the payload is launched brought to a desired location, the module is transformed into a deployed configuration.
In this configuration, the flexible shell is released and the module is inflated with a gas; usually air. As the volume within the module increases, the shell unfolds and expands. When fully inflated the shell encompasses a volume that is far greater than the comparable volume in a solid hulled craft of the same launch dimensions.
Whipple Shield technology began transitioning into softer materials such as ceramic cloth for use as sacrificial impacting and disrupting layers. In U.S. Pat. No. 6,298,765 to Dvorak, multiple layers of soft impacting materials are separated by open cell foam. The shield is comprised of an assembly of a number of impacting and separating layers that are covered and the cover is attached to the surface of a spacecraft. Each assembly is a complete shield segment that is designed to attach to the spacecraft, but not to other segments. The flexible disrupting/shocking material can, for example, include Kevlar®, Nextel® ceramic fiber cloth, and Beta Cloth™.
Another flexible Whipple Shield is described in U.S. Pat. No. 6,547,189 to Raboin, et al. The meteor orbital debris (MOD) shield is composed of flexible bumper layers with spacing layers between each bumper layer. In the Raboin patent, the MOD is not segmented in separate assemblies like the shield in the Dvorak patent, but rather is a single shield that covers the spacecraft hull. The Raboin patent was drawn to the use of the shield as part of an inflatable module.
While the aforementioned patents illustrate the use of a flexible debris shield, the shields are either one piece or a number of separate and independent shield segments.
One advantage to the present invention is the ability to piece together the gores into a connected single unit. This allows for more flexibility when installing the shield over the use of a one-piece shield.
Each gore is comprised of flexible disrupting/shocking material. A number of gores are attached one to another to form a covering for the spacecraft hull. Between each gore can be placed a spacing element, most often a type of open cell foam. A number of layers comprising the gores and spacing material may be layered upon the hull. At least the outermost gore is connected to the spacecraft to assist in keeping the shield in place. Also, the debris shield of the present invention can be used with solid and flexible hulled spacecraft.
An advantage to the use of a shield comprised of a flexible gore assembly and open cell foam is that the shield can be folded and compressed for launch and upon deployment the shield can be extended to take advantage of the Whipple Shield type of configuration. The segmented debris shield is thus applicable to solid and flexible hulled crafts.